Biochemicals, primarily polyanions like pyran copolymer, are used as immune stimulators to specifically or nonspecifically direct host immunity towards its neoplasm. These materials are used as adjuvants to customary anticancer therapy. The in vivo and in vitro aspects of these agents with respect to tumor immunology and biochemistry are being investigated in order to elucidate their mechanisms of action. Specifically, pyran copolymer (NSC-46015) is capable of beneficially prolonging life span and increasing numbers of survivors when used as an adjuvant to chemotherapy of murine leukemia. In addition, this copolymer can specifically and strongly augment antitumor immunity to L1210 leukemia after suboptimal vaccination with radiated tumor cells. The immunology of these phenomena in terms of lymphocyte and macrophage stimulation of pyran is being investigated. The interaction of pyran with isolated preparations of mouse liver nuclei with respect to stimulation of DNA synthesis and nuclear histone interaction is being studied biochemically.